The present invention relates to a film pressure plate on a camera back cover to press photographic film tightly against film guides, thereby holding the film flat in the focal plane.
To produce an image accurately formed on photographic film, it is essential to hold the film with its surface perpendicular to the optical axis and to position it within the depth of focus. For the purpose of holding the film flat in the focal plane, a pressure plate of metal such as aluminum or the like is attached to the camera back cover by means of leaf springs of stainless steel so as to press the film against guide rails upon closing the camera back cover.
Film pressure plates conventionally employed have a surface against the film, wherein an extremely large number of minute shallow indentations are provided at equal spaces so as to avoid close adhesion to the film. However, such film pressure plates gradually become loaded with dust from the exterior, and sticky residues rub off the film while using the camera at frequent intervals, with the result that the pressure plate can no longer fulfil its intended function and the film is caused to travel poorly owing to the close adhesion to the film. Furthermore, the dust and residues, if they accumulate sufficiently in the indentations so as to become solid, scratch the film surface.